In recent years, a variety of projectors have been widely used in various video applications. Phosphor wheels are usually utilized as illumination elements and cooperated with laser sources for exciting and converting one or more color lights.
Generally, a conventional phosphor wheel is loaded on a motor for rotation. Please refer to FIG. 1. FIG. 1 schematically illustrates the structure of a conventional phosphor wheel of prior art. Phosphor powder is coated on an outer rim of the substrate 10 of the conventional phosphor wheel 1 to form a phosphor rim 11. Since the laser source is fixedly projected on the same position, during the rotation the entirety of the phosphor rim 11 can be used by the laser source to excite and convert color lights, and can be used to dissipate heat simultaneously.
The beam of laser source is directly projected on the phosphor rim 11, and the heat source range 12 is indicated as dashed lines in FIG. 1. Since laser has the characteristic of high energy density, the exciting trajectory of a light spotlight spot becomes the position of high-temperature heat source, which causes poor temperature uniformity. The operational temperature of the phosphor powder is relatively high, such that the light output efficiency is decreased, and even the binder binding the phosphor powder in the phosphor rim 11 may be burnt up.
Although heat-dissipating fans or heatsinks are utilized in some product and adhered on the backside of a phosphor wheel, in this manner it will significantly increase the weight and volume of the phosphor wheel. If the volume is not enough, the effectivity of heat-dissipation is limited. Other products in the prior art are formed as having a substrate with continuously concave-convex surface structure. However, the airflow is only generated at one side of the substrate under this circumstance. The air over the front side and the backside cannot be exchanged with each other. The effectiveness of heat-dissipation is poor.
Therefore, there is a need to provide an improved phosphor wheel that enhances the effectiveness of heat-dissipation and the light output efficiency and eliminate the above drawbacks.